1. Field of the Invention
The present invention relates to a printer control apparatus having a controller for use in exchanging data between a reader and a printer thereof, and a method of controlling the same, a printer and a method of controlling the same, a reader and a method of controlling the same, and an image forming system.
2. Description of the Related Art
Conventionally, an image forming apparatus has been proposed, which is comprised of a reader section that reads an image, a printer that prints image data, and an image controller that performs image processing, stores images, and controls image data. The reader, the printer, and the image controller are configured as an integral unit.
Many of image forming apparatuses of this kind are digital copying machines that are comprised of a reader and a printer which perform processing at the same processing speed. In the case where the processing speeds of the reader and the printer are equal, the timing for starting scanning an original by the reader and the timing for starting printing by the printer are uniquely defined such that the printer starts printing data on the sheet and the reader starts scanning the original at the same time, when a sheet is fed to a print-enabling position.
In recent years, however, digital copying machines have been developed which are additionally provided with multiple functions such as a facsimile function and a PDL printing function. Some of such digital copying machines have a page memory that temporarily stores image data on a page-by-page basis, and some of such digital copying machines are called image servers and are capable of storing image data compressed in advance. Further, multifunction digital copying machines with increased productivity have been developed, and they have realized a considerable increase in the processing speed at which a reader scans an original and the processing speed at which a printer carries out printing operation.
Under the circumstances, digital copying machines have been proposed which enable efficient printing by absorbing a speed difference in the case where there is a difference in processing speed between a reader and a printer thereof.
Specifically, the data transfer speed of photoelectric conversion means such as a CCD which converts an optical image into electric image data after scanning of an original by the reader is usually higher than the data transfer speed of exposure means such as a laser which forms an image as an electrophotograph by the printer. Since thus there is a difference in the processing speed between the reader and the printer, the digital copying machines are configured to temporarily store image data from the reader in the above-mentioned page memory and then transmit the image data from the page memory to the printer in timing calculated according to a predetermined equation to absorb the difference in the processing speed.
With this arrangement, image data can be efficiently printed in such timing that transmission of image data to the printer never outpaces writing of an image by the reader.
With the trend of multi-functioning, however, digital copying machines have been developed which are comprised of a reader that reads an original and converts the read image into image data, a printer that receives the image data and prints the same on a sheet or the like, and a controller that executes an image data processing function, image data storage function, PDL function, network function, and others. These component parts are configured in separate bodies, and the controller controls respective engines of the reader and the printer via an interface common to them. With this arrangement, a plurality of readers that perform processing at different processing speeds and a plurality of printers that perform processing at different processing speeds can be connected to one controller.
In order to efficiently transfer image data from the reader to the printer via the page memory of the controller in the above described image forming apparatus, there is the necessity of acquiring respective processing speeds of a plurality of readers and a plurality of printers and calculating the timing for transmitting image data to the printers according to configurations of the readers and the printers. This requirement, however, cannot be satisfied according to the prior art.